Subband coded digital transmission system using some composite signals

A digital transmission system, for producing a replica of a digital signal comprising at least a first and a second component, comprising a transmitter and a receiver,

• wherein said transmitter comprises:
• an encoder including analysis means for filtering said digital signal to obtain subband signals for M subbands, where M>1, said subband signals including a plurality of first subband signals and a plurality of second subband signals from said first component and second component respectively,
• signal combination means for combining m.sub.1 of said first subband signals respectively with m.sub.1 of said second subband signals from corresponding subbands to obtain m.sub.1 composite subband signals, where 1<m.sub.1 <M,
• signal generator means for generating an indicator signal indicating which said first and second subband signals are combined, and
• transmission means for transmitting said indicator signal, said composite subband signals, and subband signals which were not combined, and
• the receiver comprises:
• receiving means for receiving the signals which have been transmitted,
• detection means for detecting said indicator signal,
• derivation means responsive to the received indicator signal, for producing, from the received composite subband signals, derived subband signals related to m.sub.1 of said first subband signals and m.sub.1 of said second subband signals, and
• a decoder including synthesis means for combining said derived subband signals and the received subband signals which were not combined, to produce said replica of the digital signal.

A transmitter, for transmitting signals representative of a digital signal comprising at least a first component and a second component, over a transmission medium, comprising:

• an encoder including analysis means for altering said digital signal to obtain a plurality of sub-signals, including at least a first sub-signal and a second sub-signal from said first component and said second component respectively,
• signal combination means for combining said first sub-signal and said second sub-signal to obtain a composite sub-signal,
• signal generator means for generating an indicator signal indicating that said first sub-signal and said second sub-signal are combined,
• transmission means for transmitting said indicator signal, said composite sub-signal, and sub-signals which have not been combined.